1. Field of the Invention
The present invention relates to a method for distributing contents and a system for use in such a method. More particularly, the invention relates to a method for distributing contents by use of storage unit, and a system used in such a method.
2. Description of the Related Art
As a system distributing contents used via a network, Hybrid P2P system (“Internet Magazine”, Impress Publishing Co., January 2001, pp. 234-235) is known. The Hybrid P2P (HP2P) System is described as follows in the column “Features of S/C System and P2P System”, on page 235 of this magazine. “In many cases, information to be shared is located at clients, and servers manage only the location of information. Information is exchanged one to one in a redirected form from the result of retrieval of the servers. This may be called a ‘pseudo-S/C system’, and user authentication by a server is possible. The protocol stack on TCP/IP is unique to each service, and is characterized by an aperiodic update of information. While the server regulates the service player, the information self-reproduces”.
Such a system comprises a plurality of client (client computers) and a server. At a point in time of turn-on at a client, the client transmits a list of kinds of data (contents) held by the client to the server. Upon turn-off of power, each client notifies the server of the intention to turn off power. The server manages the list of clients currently holding data of various kinds with reference to inspection of the kind of transmitted data.
When a client is to receive data of a particular kind from another client, steps to be taken are as follows. First, the client wishing to receive data inquires the server from which client the data should be received. This inquiry is accomplished in the following procedure:
(1) The client wishing to receive data transmits the information which specifies the data to be received to the server.
(2) The server selects a client the closest to the client wishing to receive data from among the list of clients holding the data specified by the above-mentioned specifying information. Information showing the thus selected client is notified to the client wishing to receive data.
Then, the client wishing to receive data issues a data transmitting request to the client notified in (2) above. As a result, it is possible to receive data of the specified kind from the client having received the notice in (2) above.
An example of contents distribution by use of such a P2P (peer-to-peer) system is reported in (SIIA PEER-TO-PEER WHITE PAPER, published by Software & Information Industry Association).
The aforementioned distributing method has various problems regarding the system framework itself in that a client holds data, and the client transmits data to the requesting client.
A first problem is that clients selectable as data transmitting locations are limited to clients of which power is turned on. That is, clients of which power is currently turned off cannot be selected as a transmitting client. For example, even though there is a client the closest to the client requesting transmission of data (requesting client), holding the requested data, if it is in turn-off state of power, the data would be transmitted from another client holding the same data. In this case, the network distance between the clients exchanging the data may be longer. As a result, the total amount of the network band consumed upon data exchange becomes larger.
A second problem relates to billing. When distributing data, in general, a service use fee and a data use fee (contents use fee) are charged for data distribution. In the above-mentioned data distributing method, however, billing is not easy. In order to carry out billing, it is necessary, after conducting data transmission and receiving on the client side, to transmit an execution completion notice of data receipt from the client to the billing server. This transmission is however performed by an application which receives data, operating on the client. As a result, an easy avoidance of billing becomes possible by using means such as manipulation of the application.